LONDON, Aug 14 (Reuters) - British insurer Admiral on Wednesday posted a 4% rise in pretax profit in the first half of the year, boosted by an increase in customers in its UK business and a swing to profit for its home insurance unit.

Admiral, one of Britain’s largest motor insurers, said pretax profit rose to 220 million pounds ($265.23 million) from 212 million pounds last year.

Profit from its UK home insurance business swung to a profit of 4.2 million pounds from a loss of 1.9 million pounds.

A recent UK rule change requiring insurers in Britain to set aside more money than they expected to compensate the victims of serious car crashes, had cost 33.3 million pounds in the first half of the year, it said in a statement.

The total impact of the change in the discount rate, or ‘Ogden Rate’, was expected to be between 50 and 60 million pounds, the insurer said.

“Profit growth, even if modest, is more exciting considering the £33 million Ogden headwind,” said David Stevens, group chief executive officer. ($1 = 0.8295 pounds) (Reporting by Lena Masri; editing by Simon Jessop)